There's lots of stuff but you need to reduce your local noise to hear some of it. A loop antenna helps enormously. Navtex is fairly easy to receive and you can download a free decoder from't'internet. Below 150kHz there's all manner of time and frequency standards and even encrypted submarine comms going all the way down to a few kHz. Once or twice a year, the SAQ 17.2 kHz TX comes on from Sweden. This is an ancient 'alternator' transmitter, just a big RF-generating mechanical AC generator putting about 80 kW up the huge vertical antenna. A shot of Grimeton as it appears on my SDR fed from a homebrew loop antenna and an audio snip of it as received on the same set up: The bigger peaks around 20-22 kHz are sub comms stations.

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